EP0468548B1

EP0468548B1 - Actuator with energy recovery return

Info

Publication number: EP0468548B1
Application number: EP91200820A
Authority: EP
Inventors: Frederik Erickson; William Richeson
Original assignee: Magnavox Electronic Systems Co
Current assignee: Magnavox Electronic Systems Co
Priority date: 1990-07-24
Filing date: 1991-04-09
Publication date: 1996-07-10
Anticipated expiration: 2011-04-09
Also published as: EP0468548A2; DE69120736T2; CA2040379A1; US5022359A; JPH0719205A; DE69120736D1; EP0468548A3

Description

The present invention relates to an asymmetrical bistable pneumatically powered actuator mechanism comprising a housing divided into a first chamber and a second chamber by a mechanism portion, a replenishable source of compressed air alternately connectable to the first chamber for causing translation of the mechanism portion in one direction, air being compressed in the second chamber during translation of the mechanism portion in said one direction for slowing the mechanism portion translation in said one direction, and means for temporarily preventing reversal of the direction of translation of the mechanism portion when the motion of the mechanism portion in said one direction slows to a stop, wherein the mechanism portion includes a hydraulic piston and the means for temporarily preventing reversal include the hydraulic piston, a hydraulic cylinder in which the hydraulic piston reciprocates and means for admitting hydraulic fluid to said hydraulic cylinder during translation of the mechanism portion in said one direction, said means for admitting hydraulic fluid closing when the motion of the mechanism portion slows to a stop to temporarily prevent the egress of the hydraulic fluid from the hydraulic cylinder.
The prior art has recognized numerous advantages which might be achieved by replacing the conventional mechanical cam actuated valve arrangements in internal combustion engines with other types of valve opening mechanisms which could be controlled in their opening and closing as a function of engine speed as well as engine crankshaft angular position or other engine parameters.
For example, in United States Patent 4,945,870 entitled VEHICLE MANAGEMENT COMPUTER filed in the name of William E. Richeson on July 29, 1988 there is disclosed a computer control system which receives a plurality of engine operation sensor inputs and in turn controls a plurality of engine operating parameters including ignition timing and the time in each cycle of the opening and closing of the intake and exhaust valves among others.
U.S. Patent 4,009,695 discloses hydraulically actuated valves in turn controlled by spool valves which are themselves controlled by a dashboard computer which monitors a number of engine operating parameters. This patent references many advantages which could be achieved by such independent valve control, but is not, due to its relatively slow acting hydraulic nature, capable of achieving these advantages. The patented arrangement attempts to control the valves on a real time basis so that the overall system is one with feedback and subject to the associated oscillatory behaviour.
U.S. Patent 4,700,684 suggests that if freely adjustable opening and closing times for inlet and exhaust valves is available, then unthrottled load control is achievable by controlling exhaust gas retention within the cylinders.
Substitutes for or improvements on conventional cam actuated valves have long been a goal. In the Richeson United States Patent 4,794,890 entitled ELECTROMAGNETIC VALVE ACTUATOR, there is disclosed a valve actuator which has permanent magnet latching at the open and closed positions. Electromagnetic repulsion may be employed to cause the valve to move from one position to the other. Several damping and energy recovery schemes are also included.
In United States Patent 4,878,464, entitled PNEUMATIC ELECTRONIC VALVE ACTUATOR, filed February 8, 1988 in the names of William E. Richeson and Frederick L. Erickson and assigned to the assignee of the present application there is disclosed a somewhat similar valve actuating device which employs a release type mechanism rather than a repulsion scheme as in the previously identified U.S. Patent. The disclosed device in this application is a jointly pneumatically and electromagnetically powered valve with high pressure air supply and control valving to use the air for both damping and as one motive force. The magnetic motive force is supplied from the magnetic latch opposite the one being released and this magnetic force attracts an armature of the device so long as the magnetic field of the first latch is in its reduced state. As the armature closes on the opposite latch, the magnetic attraction increases and overpowers that of the first latch regardless of whether it remains in the reduced state or not.
The forgoing as well as a number of other related applications all assigned to the assignee of the present invention and filed in the name of William E. Richeson or William E. Richeson and Frederick L. Erickson are summarized in the introductory portions of United States Patent 4,875,441 filed in the names of Richeson and Erickson on January 6, 1989 and entitled ENHANCED EFFICIENCY VALVE ACTUATOR.
Many of the later filed above noted cases disclose a main or working piston which drives the engine valve and which is, in turn powered by compressed air. The power or working piston which moves the engine valve between open and closed positions is separated from the latching components and certain control valving structures so that the mass to be moved is materially reduced allowing very rapid operation. Latching and release forces are also reduced. Those valving components which have been separated from the main piston need not travel the full length of the piston stroke, leading to some improvement in efficiency. Compressed air is supplied to the working piston by a pair of control valves with that compressed air driving the piston from one position to another as well as typically holding the piston in a given position until a control valve is again actuated. The control valves are held closed by permanent magnets and opened by pneumatic force on the control valve when an electrical pulse to a coil near the permanent magnet neutralizes the attractive force of the magnet.
In the devices of these applications, air is compressed by piston motion to slow the piston (dampen piston motion) near the end of its stroke and then that air is abruptly vented to atmosphere. When the piston is lowed or damped, its kinetic energy is converted to some other form of energy and in cases such as dumping the air compressed during damping to atmosphere, that energy is simply lost. U.S. Patents 4,883,025 and 4,831,973 disclose symmetric bistable actuators which attempt to recapture some of the piston kinetic energy as either stored compressed air or as a stressed mechanical spring which stored energy is subsequently used to power the piston on its return trip. In either of these patented devices, the energy storage device is symmetric and is releasing its energy to power the piston during the first half of each translation of the piston and is consuming piston kinetic energy during the second half of the same translation regardless of the direction of piston motion.
An electronically controlled pneumatically powered actuator as described in our U.S. Patent No. 4,825,528 has demonstrated very rapid transit times and infinite precise controllability. Devices constructed in accordance with this patent are capable of obtaining optimum performance from an internal combustion engine due to their ability to open and then independently close the poppet valves at any selectable crank shaft angles. In this prior patented arrangement, a source of high pressure air is required for both opening and for closing the valves. Moreover, such devices require a certain amount of duplication of structure in that symmetrical propulsion, exhaust air release, and regulated latching pressure (damping air) arrangements are needed. In this prior art configuration, substantially the same volume of air must be used to close the valve as was required to open it.
An asymmetrical bistable pneumatically powered actuator mechanism as mentioned in the opening paragraph is known from DE-A-31 39 399. The known actuator mechanism comprises a first and a second chamber, in which air is compressed during translation of the mechanism portion in a first direction and in a second direction opposite to the first direction, respectively. The known actuator mechanism is provided with a hydraulic piston, which is reciprocable with the mechanism portion and is bounded by two hydraulic chambers. The hydraulic chambers are interconnected via two one-way check valves each including means operable on command for opening the relevant one-way check valve, one of the check valves allowing free oil flow from a first one of the hydraulic chambers into the other hydraulic chamber but blocking oil flow from the other hydraulic chamber into the first hydraulic chamber, and the other of the check valves allowing free oil flow from the other hydraulic chamber into the first hydraulic chamber but blocking oil flow from the first hydraulic chamber into the other hydraulic chamber. By the use of said two one-way check valves the mechanism portion is blocked automatically in its two extreme positions during a predetermined period until the relevant check valve is opened on command. The oil supplied to the hydraulic chambers is pressurized via a fluid conduit by a hydraulic pump. A disadvantage of this known actuator mechanism is that, besides a high pressure air supply system, the known actuator mechanism is also provided with a high pressure hydraulic fluid supply system comprising said hydraulic pump. This leads to a construction which is rather complicated and therefore prone to malfunction.
Among the several objects of the present invention may be noted the provision of an actuator which is propelled in one direction in accordance with known techniques, but then the actuator is locked or latched against the force of retained compressed air for a controlled length of time; the provision of an actuator in accordance with the previous object which, at the prescribed time, deactivates the latch, releasing an actuating piston under the force of the retained compressed air, moves in the opposite direction back to its initial position; the provision of an actuator in accordance with either of the previous objects with alternative schemes for latching and unlatching the piston; the provision of latching schemes for an actuator in accordance with the previous object which adequately and reliably hold the piston against the strong force of the retained compressed air while releasing quickly to allow a very fast return of the actuator piston to its initial position; the provision of proper engine valve seating pressure by the application of a controlled latching force to the valve piston; and the provision of a relatively simple and reliable construction of the actuator mechanism. These as well as other objects and advantegeous features of the present invention will be in part apparent and in part pointed out hereinafter.
The asymmetrical bistable pneumatically powered actuator mechanism according to the invention is for these purposes characterized in that said means for admitting comprise a hydraulic chamber for the supply of the hydraulic fluid to the hydraulic cylinder, the hydraulic fluid in said hydraulic chamber being pressurized by pressurized air which is present in an air chamber communicating with said hydraulic chamber. In this way, the actuator mechanism according to the invention can dispense with a high pressure hydraulic fluid supply system and only needs a high pressure air supply system. Therefore, the actuator mechanism according to the invention has a relatively simple and reliable construction.
Make-up air may be supplied to the chamber to compensate for frictional, leakage and other losses or variations as well as to maintain the piston latching force at the required level when the mechanism portion is in the initial position. This make-up air may be supplied via a one-way inlet valve mounted between said chamber and said intermediate air pressure source. The mechanism portion typically includes a reciprocable piston having first, second and third working faces each defining a portion of corresponding first, second and third variable volume chambers the volumes of which vary linearly with piston position. The chamber in which air is compressed being the first chamber, the second chamber cooperating with the replenishable source of high pressure hydraulic fluid for causing translation of the mechanism portion, and the third chamber comprising a portion of the arrangement for temporarily preventing reversal of the piston motion.

BRIEF DESCRIPTION OF THE DRAWING

Figure 1 is a view in cross-section of a valve actuating mechanism in its initial or valve-closed position illustrating the invention in one form;
Figure 2 is a view in cross-section similar to Figure 1, but illustrating the mechanism having transitioned half way toward its second or valve-open position;
Figure 3 is a view in cross-section similar to Figure 1, but illustrating the mechanism having transitioned three-quarters of the way toward its second position;
Figure 4 is a view in cross-section similar to Figure 1, but illustrating the mechanism having transitioned completely to its valve-open position;
Figure 5 is a view in cross-section similar to Figure 1 again illustrating the mechanism in its valve-open position, but at the moment the latch is released;
Figure 6 is a view in cross-section similar to Figure 1, but illustrating the mechanism having transitioned half way back toward its valve-closed position;
Figure 7 is a view in cross-section similar to Figure 1, but illustrating the mechanism having transitioned three-quarters of the way back toward its valve-closed position; and
Figure 8 is a view in cross-section similar to Figure 1, but illustrating the mechanism having reached its initial position.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawing.
The exemplifications set out herein illustrate a preferred embodiment of the invention in one form thereof and such exemplifications are not to be construed as limiting the scope of the disclosure or the scope of the invention in any manner.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The overall valve actuator is illustrated in cross-section in Figure 1 in conjunction with which various component locations and functions in moving a poppet valve or other component (not shown) from a first position (in which the poppet valve is seated) to a second position (in which the poppet valve is fully open) will be described. Motion in the opposite direction will be quite different and will be described subsequently. Figure 1 illustrates the actuator at rest before any command is given to energize the unit. The actuator includes a shaft or stem 11 which may form a part of or connect to an internal combustion engine poppet valve. The actuator also includes a low mass reciprocable piston 13, and a reciprocating or sliding control valve member 15 enclosed within a housing 19. The piston and control valve reciprocate along the common axis 12. The control valve member 15 is latched in one (the closed) position by permanent magnet 21 and may be dislodged from that latched position by energization of coil 25. The permanent magnet latching arrangement also includes ferromagnetic latch plate 20 which is an iron or similar ferromagnetic member attached to and movable with the air control valve member 15. The control valve member or shuttle valve 15 cooperates with the cylindrical end portion 26 of piston 13 as well as with the housing 19 to achieve the various porting functions during operation. The housing 19 has a high pressure inlet port 39, a low pressure outlet port 41 and an intermediate pressure port extending from the sidewall aperture 43. The low pressure may be about atmospheric pressure while the intermediate pressure is about 70 kPa (ten psi.) above atmospheric pressure and the high pressure is on the order of 700 kPa (100 psi.) gauge pressure.
When the valve actuator is in its initial state with piston 13 in the extreme leftward position and with the air control valve 15 latched closed, the annular abutment end surface 29 of the control valve seals against an O-ring 31. This seals the pressure in cavity 39 and prevents the application of any moving force to the main piston 13. In this position, the main piston 13 is being urged to the left (latched) by the pressure in cavity or chamber 35 which is greater than the pressure in chamber or cavity 37. This latching pressure in chamber 35 is maintained by an intermediate, e.g., 70 kPa (10 psi.), pressure source coupled to the inlet of the one-way check valve 17. When it is desired to open, e.g., an associated engine intake or exhaust valve, coil 25 is energized and the current flow therein induces a magnetic field opposing the field of the permanent magnet 21. With the magnetic latching force on plate 20 thus essentially neutralized, the unbalanced force of the high pressure air against surface 29 moves the control valve 15 leftward as viewed from the position of Figure 1 to the position illustrated in Figure 2 where an annular opening has formed near the O-ring 31 between the control valve 15 and edge 48 of the housing 19 which opening has allowed high pressure air from source chamber 39 to enter chamber 37 powering the piston toward the right. In Figure 2, the piston 13 has moved from its leftmost position nearly half the distance to its other bistable position. As piston 13 moves toward the right, it compresses air and stores energy in chamber 35. As the air in chamber 35 is compressed, slow down and damping of piston motion occurs. In Figure 3, the piston 13 has uncovered the intermediate or "latching" pressure aperture 43 releasing any unexpanded air to atmosphere and removing the driving force from the piston. The air captured in chamber 35 is being compressed to dampen or slow the piston motion. At the point where the energy of compression of air in chamber 35 plus the system friction is the same as the energy expended by expansion of the compressed air in chamber 37, the piston comes to rest in its rightmost
(engine valve open) or second position as shown in Figure 4. Were the piston not captured at this time, the compressed air in chamber 35 would simply cause the piston to rebound and retrace its path back to the valve closed position, however, an automatic latch grabs the piston and holds it against the high force of the compressed air in the valve-open position until commanded to release it. In Figure 6, the piston has been released allowing the compressed air to expand driving the piston back toward the initial position.
In the preferred form, the latch for capturing the piston incorporates a fixed location hydraulic cylinder together with a piston connected to and movable with the powered piston 13 and shaft assembly. The fixed cylinder and piston are configured so that as the main power piston 13 is driven from the first to the second position by source air pressure as described above, the hydraulic piston pulls a relatively non-compressible fluid through an open one-way valve into the cylinder. This fluid can be pressurized to help overcome any restrictions which might hinder its entry into the cylinder and to limit any tendency for the fluid to cavitate leaving an undesirable vacuum or void in the cylinder. The fluid fills the cylinder volume up to the point where the main power piston reaches the second position. When the main piston begins to reverse direction under the urging of the recently compressed air, the one-way valve closes to retain the fluid in the cylinder halting movement of the main piston. The fluid pressure in the cylinder holds the one-way valve closed, thus, the main piston will remain at the second position until a command is given to release the latch. The release function is provided by an electromagnetic solenoid operated plunger which physically displaces the one-way valve from its closed position allowing the trapped fluid to flow back out of the hydraulic cylinder. When the fluid is allowed to empty from the cylinder, the high pressure air trapped in chamber 35 rapidly pushes the main piston from the second position back to the first position.
Ball 23 and valve seat 27 function as a one-way or check valve. In the transition between Figures 1 and 2, the ball 23 has been lifted off the valve seat 27 allowing fluid from chamber 33 to flow past the ball 23 and into the expanding chamber or cylinder 45. Chamber 47 is filled with pressurized air and effectively pressurizes the fluid in chamber 33 by way of a flexible membrane 49 to aid in the transfer of fluid into the cylinder 45. A small amount of make-up air may be added to chamber 47 by way of air inlet 46. Note that the membrane 49 is bowed radially outwardly in Figure 1, when chamber 33 is full of fluid, reaches a neutral position in Figure 2, and is bowed radially inwardly in Figure 3 where much of the fluid has exited the chamber 33 and entered into chamber 45.
In Figure 2, the main piston is just uncovering the port 43 while in Figure 3 this port is well open and the pressurized air in chamber 37 is vented to atmosphere removing the rightward pneumatic driving force from the piston 13. Figure 3 illustrates the piston position as it is slowing down and compressing air in chamber 35. In Figure 4, the piston has reached its second position and the air in chamber 35 is highly compressed. The high force on the piston due to this high pressure air in chamber 35 causes the fluid in cylinder 45 to attempt to exit past the ball 23 of the check valve causing the ball to close and seat firmly on the annular seal or seat 27. When the check valve closes, fluid entrapped in chamber 45 holds the piston 13 in its rightmost or valve-open position against the pressure of the air compressed in chamber 35.
A comparison of Figures 4 and 5 will illustrate the manner in which the valve actuator responds to a command to return to the first position and close the engine valve. Upon command, a current is caused to flow in the coil 51 attracting ferromagnetic plate 53 to close and moving the centrally located plunger 55 sharply into engagement with the ball 23 unseating the ball from the annular seal 27 and allowing the fluid to exit chamber 45 and flow back into chamber 33. Note that in the sequence of Figures 5-8, the membrane 49 swells radially outwardly as chamber 33 is refilled. Note also that in the sequence of Figures 5-8 the ball is held in its open position by the plunger 55. With fluid free to exit chamber 45, the latching is effectively nullified and the highly compressed air in chamber 35 forces the piston leftwardly as viewed toward its initial or first position. When the piston has completed the trip to its initial position as in Figure 8, the solenoid 51 may thereafter be deenergized allowing spring 57 to return ball 23 to rest against seat 27 and the device will again assume the configuration shown in Figure 1.
As thus far described, actuator motion toward the valve-open position is slowed or damped by the compressing of air in chamber 35. By capturing the piston just as it reaches a complete stop, the energy of piston motion has been converted into and is stored as potential energy. This potential energy is later used (when the piston is released) to power the piston back to the valve-closed position. Since internal combustion engine valves spend more time in the closed than in the open position, the high pressure compressed air need only be held a short time, however, it is possible to instead use the compressed air to drive the piston from the valve-closed to the valve-open position with perhaps some sacrifice in the form of leakage losses. Such leakage could be either air or hydraulic latching fluid and could occur at a number of locations including the latching pressure air inlet check valve 17, around annular piston seal 59, past the main shaft seal 63, around the small annular piston seal 61, or between ball 23 and its seat 27.
There has been thus far described a method of storing potential energy in the form of air compressed in a chamber 35 by a piston 13 which includes driving the piston in a direction (to the right as viewed) to compress air in the chamber, and at the appropriate time, removing the piston drive by closing the valve 15 and allowing the piston to be slowed by the force of the air being compressed in chamber 35. The piston is captured near the time when its motion has slowed to a stop and prior to any significant leftward motion in a direction opposite the air compressing direction. The piston is subsequently released on command allowing the compressed air stored energy to propel the piston back toward the left as viewed in a direction opposite the air compressing direction.

Claims

An asymmetrical bistable pneumatically powered actuator mechanism comprising a housing (19) divided into a first chamber (37) and a second chamber (35) by a mechanism portion (13), a replenishable source (39) of compressed air alternately connectable to the first chamber (37) for causing translation of the mechanism portion (13) in one direction, air being compressed in the second chamber (35) during translation of the mechanism portion (13) in said one direction for slowing the mechanism portion (13) translation in said one direction, and means (23, 33, 45, 47, 49) for temporarily preventing reversal of the direction of translation of the mechanism portion (13) when the motion of the mechanism portion (13) in said one direction slows to a stop, wherein the mechanism portion (13) includes a hydraulic piston and the means (23, 33, 45, 47, 49) for temporarily preventing reversal include the hydraulic piston, a hydraulic cylinder (45) in which the hydraulic piston reciprocates and means (23, 33, 47, 49) for admitting hydraulic fluid to said hydraulic cylinder (45) during translation of the mechanism portion (13) in said one direction, said means (23, 33, 47, 49) for admitting hydraulic fluid closing when the motion of the mechanism portion (13) slows to a stop to temporarily prevent the egress of the hydraulic fluid from the hydraulic cylinder (45), characterized in that said means (23, 33, 47, 49) for admitting comprise a hydraulic chamber (33) for the supply of the hydraulic fluid to the hydraulic cylinder (45), the hydraulic fluid in said hydraulic chamber (33) being pressurized by pressurized air which is present in an air chamber (47) communicating with said hydraulic chamber (33).
An asymmetrical bistable pneumatically powered actuator mechanism as claimed in Claim 1, characterized in that the pressurized air in the air chamber (47) pressurizes the hydraulic fluid in the hydraulic chamber (33) by way of a flexible membrane (49).
An asymmetrical bistable pneumatically powered actuator mechanism as claimed in Claim 1 or 2, characterized in that means (51, 53, 55) are provided which are operable on command to disable the temporarily preventing means (23, 33, 45, 47, 49) freeing the mechanism portion (13) to move under the urging of the air compressed in the second chamber (35) in the direction opposite said one direction.
An asymmetrical bistable pneumatically powered actuator mechanism as claimed in Claim 3, characterized in that said means (51, 53, 55) operable on command comprise solenoid means (51) which are operable on command to hold open the means (23, 33, 47, 49) for admitting thereby allowing the egress of hydraulic fluid from the hydraulic cylinder (45) and motion of the mechanism portion (13) in the direction opposite said one direction.
An asymmetrical bistable pneumatically powered actuator mechanism as claimed in any one of the preceding Claims, characterized in that means (17) are provided for supplying make-up air to the second chamber (35) to compensate for frictional and other losses.
An asymmetrical bistable pneumatically powered actuator mechanism as claimed in any one of the preceding Claims, characterized in that the mechanism portion (13) includes a reciprocable piston (13) having first, second and third working faces each defining a portion of corresponding first, second and third variable volume chambers (35, 37, 45) the volumes of which vary linearly with piston (13) position, the first chamber (37) being the first variable volume chamber, the second chamber (35) being the second variable volume chamber, and the third variable volume chamber (45) comprising a portion of the means (23, 33, 45, 47, 49) for temporarily preventing reversal.
An asymmetrical bistable pneumatically powered actuator mechanism as claimed in any one of the preceding Claims, characterized in that an inlet valve (43) is provided for supplying a latching air pressure to the second chamber (35) in which air is compressed at least when the piston (13) is in the initial position to latch the piston (13) in the initial position until piston (13) translation is initiated by the source of compressed air.